Method and system for asymmetric operation in a network node in an energy efficient network

ABSTRACT

An Ethernet network comprising multi-rate link partners that may be operable to communicate symmetrically and/or asymmetrically via any of a plurality of channels. The multi-rate link partners may monitor one or more factors that may affect their power consumption and/or energy efficiency. During operation, an uplink and/or downlink communication rate may be configured, based on the monitoring, to enable asymmetrical data rate operation. The monitored factors may comprise prior or current data rates, bit error rate, packet error rate, latency, queued data and/or tasks, for example. The multi-rate link partners may comprise a twisted pair PHY, an optical PHY or a backplane PHY. In order to reduce power consumption and/or improve energy efficiency, one or more of the uplink communication rate and/or the downlink communication rate may be lowered. The power consumption may be reduced for a multi-rate PHY, a host computer and/or a MAC controller.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of U.S. patent application Ser. No.12/235,368, filed on Sep. 22, 2008.

Patent application Ser. No. 12/235,368 claims priority to, and claimsthe benefit of U.S. Provisional Application Ser. No. 61/014,195 filed onDec. 17, 2007.

Patent application Ser. No. 12/235,368 also claims priority to, andclaims the benefit of U.S. Provisional Application Ser. No. 61/094,626filed on Sep. 5, 2008.

This patent application also makes reference to:

-   U.S. patent application Ser. No. 12/235,345 filed on Sep. 22, 2008;-   U.S. patent application Ser. No. 12/235,391 filed on Sep. 22, 2008;-   U.S. patent application Ser. No. 12/235,410 filed on Sep. 22, 2008;    and-   U.S. patent application Ser. No. 12/235,506 filed on Sep. 22, 2008.

Each of the above stated applications is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to networking. Morespecifically, certain embodiments of the invention relate to a methodand system for asymmetric operation in a network node in an energyefficient Ethernet network.

BACKGROUND OF THE INVENTION

With the increasing popularity of electronics such as desktop computers,laptop computers, and handheld devices such as smart phones and PDA's,communication networks, and in particular Ethernet networks, arebecoming an increasingly popular means of exchanging data of varioustypes and sizes for a variety of applications. In this regard, Ethernetnetworks are increasingly being utilized to carry, for example, voice,data, and multimedia. Accordingly more and more devices are beingequipped to interface to Ethernet networks.

As the number of devices connected to data networks increases and higherdata rates are required, there is a growing need for new transmissiontechnologies which enable higher data rates. Conventionally, however,increased data rates often result in significant increases in powerconsumption.

New transmission technologies enable higher transmission rates over aplurality of infrastructures such as copper cabling, optical fiber andbackplane connectivity, for example, KR and KX4 copper backplanephysical media. Various efforts exist in this regard, includingtechnologies that enable transmission rates that may even reach 100Gigabit-per-second (Gbps) data rates over existing cabling.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present invention as set forth inthe remainder of the present application with reference to the drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an Ethernet connection between alocal link partner and a remote link partner, in accordance with anembodiment of the invention.

FIG. 2 is a block diagram illustrating an exemplary Ethernet overtwisted pair PHY device architecture comprising a multi-rate physicalblock, in accordance with an embodiment of the invention.

FIG. 3A is a block diagram illustrating asymmetric data rates enablingreduced power consumption and improved energy efficiency, in accordancewith an embodiment of the invention.

FIG. 3B is a block diagram of an exemplary system that may utilizeasymmetric data rates to reduce power consumption, in accordance with anembodiment of the invention.

FIG. 4 is a flow chart illustrating exemplary steps for communicatingbetween link partners via one or more channels utilizing asymmetric datarates, in accordance with an embodiment of the invention.

FIG. 5 is a data flow diagram illustrating an exemplary method forchanging data rate in an asymmetric network configuration, in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor asymmetric operation in a network node in an energy efficientEthernet network. Exemplary aspects of the invention, the Ethernetnetwork may comprise network nodes that may be, for example, multi-ratelink partners coupled via an Ethernet link. The Ethernet link maycomprise one or more channels over which the multi-rate link partnersmay communicate. The multi-rate link partners may be operable tocommunicate over any of the channels via symmetric and/or asymmetricdata rates. In addition, the multi-rate link partners may be operable tomonitor one or more factors that may affect their power consumptionand/or energy efficiency. The monitored factors may comprise, forexample, prior or current data rates, bit error rate (BER), packet errorrate (PER) and/or latency. In addition, one or more factors that mayaffect power consumption and/or energy efficiency may comprise one ormore of data load, queue depths, queue change rates, tasks assigned busoperations and/or OSI layer two and above control policy. Based on themonitoring, an uplink communication rate and/or a downlink communicationrate may be configured for asymmetrical operation via any of theplurality of channels.

In accordance with an embodiment of the invention, the multi-rate linkpartners may comprise, for example, a twisted pair PHY, an optical PHYor a backplane PHY. In order to, for example, reduce power consumptionand/or improve energy efficiency, one or more of the uplinkcommunication rate and/or the downlink communication rate may belowered. The communication rate may be transitioned to a lower or higherdata rate at, for example, designated byte boundaries and/or at LDPCframe boundaries. In this manner, the power consumption may be reducedwithin one or both link partners for one or more of a multi-rate PHY, ahost computer and/or a MAC controller.

In some embodiments of the invention, the multi-rate link partners maycomprise a multimedia system wherein high bandwidth multimedia data maybe transmitted in a first direction at a first data rate, for example,from an uplink multimedia server to a downlink client. Corresponding lowbandwidth control information may be transmitted in a second directionat a second data rate from the downlink client to the uplink multimediaserver. Data rate in one direction may drop to zero while data rate inthe opposite direction may be at a full rate or an intermediate rate forexample. In addition to reducing power consumption, various embodimentsof the invention may, for example, provide reduced crosstalk and/or EMIand improvements in bit error rate and/or latency.

FIG. 1 is a block diagram illustrating an Ethernet connection between alocal link partner and a remote link partner, in accordance with anembodiment of the invention. Referring to FIG. 1, there is shown asystem 100 that comprises a local link partner 102 and a remote linkpartner 104. The local link partner 102 and the remote link partner 104may communicate via a cable 112. Throughout this document, the cable 112may also be referred to as the Ethernet link 112, for example. In anexemplary embodiment of the invention, the cable 112 may comprise up tofour or more channels, each of which may, for example, comprise anunshielded twisted pair (UTP). The local link partner 102 and the remotelink partner 104 may communicate via two or more channels comprising thecable 112. For example, Ethernet over twisted pair standards 10BASE-Tand 100BASE-TX may utilize two pairs of UTP while Ethernet over twistedpair standards 1000BASE-T and 10GBASE-T may utilize four pairs of UTP.

In an exemplary embodiment of the invention, the link partners 102and/or 104 may comprise a twisted pair PHY capable of operating at oneor more standard rates such as 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps(10BASE-T, 100GBASE-TX, 1GBASE-T, and/or 10GBASE-T); potentiallystandardized rates such as 40 Gbps and 100 Gbps; and/or non-standardrates such as 2.5 Gbps and 5 Gbps.

In an exemplary embodiment of the invention, the link partners 102and/or 104 may comprise a backplane PHY capable of operating at one ormore standard rates such as 10 Gbps (10GBASE-KX4 and/or 10GBASE-KR);potentially standardized rates such as 40 Gbps and 100 Gbps and/ornon-standard rates such as 2.5 Gbps and 5 Gbps such as 40 Gbps and 100Gbps; and/or non-standard rates such as 2.5 Gbps and 5 Gbps that may beutilized as intermediate or sub rates for a 10 Gbps PHY for example.

In an exemplary embodiment of the invention, the link partners 102and/or 104 may comprise an optical PHY capable of operating at one ormore standard rates such as 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps;potentially standardized rates such as 40 Gbps and 100 Gbps; and/ornon-standardized rates such as 2.5 Gbps and 5 Gbps. In this regard, theoptical PHY may be a passive optical network (PON) PHY.

The local link partner 102 may comprise a host 106 a, a medium accesscontrol (MAC) controller 108 a, and a PHY device 110 a. The remote linkpartner 104 may comprise a host 106 b, a MAC controller 108 b, and a PHYdevice 110 b. Notwithstanding, the invention is not limited in thisregard. In various embodiments of the invention, the link partner 102and/or 104 may comprise, for example, computer systems or audio/video(NV) enabled equipment. In this regard, the A/V enabled equipment may,for example, comprise, a microphone, an instrument, a sound board, asound card, a video camera, a media player, a graphics card, or otheraudio and/or video device. Additionally, the link partners 102 and 104may be enabled to utilize Audio/Video Bridging and/or Audio/videobridging extensions (collectively referred to herein as AVB) for theexchange of multimedia content and associated control and/or auxiliarydata.

In various embodiments of the invention, the remote link partner 104 maybe an uplink partner, for example a media server, a data center serveror top of rack switch that may transmit data to the local link partner102. In this manner, the local link partner 102 may be a downlink linkpartner, for example, a personal computer (PC), television orset-top-box. The uplink remote partner 104 may transmit high data ratetraffic such as video and/or audio data whereas the downlink localpartner 102 may transmit low rate signaling traffic. Accordingly, datarates between the uplink remote partner 104 and downlink local partner102 may be asymmetrical.

The PHY devices 110 a and 110 b may each comprise suitable logic,circuitry, and/or code that may enable communication, for example,transmission and/or reception of data, between the local link partner102 and the remote link partner 104. The PHY devices 110 a and 110 b maysupport, for example, Ethernet operations. The PHY devices 110 a and 110b may enable communications, such as 10 Mbps, 100 Mbps, 1000 Mbps (or 1Gbps), 2.5 Gbps, 4 Gbps, 5 Gbps, 10 Gbps or 40 Gbps or 100 Gbps forexample. In this regard, the PHY devices 110 a and 110 b may supportstandard-based data rates and/or non-standard data rates. Moreover, thePHY devices 110 a and 110 b may support standard Ethernet link lengthsor ranges of operation and/or extended ranges of operation. The PHYdevices 110 a and 110 b may enable communication between the local linkpartner 102 and the remote link partner 104 by utilizing a linkdiscovery signaling (LDS) operation that enables detection of activeoperations in the other link partner. In this regard the LDS operationmay be configured for supporting a standard Ethernet operation and/or anextended range Ethernet operation. The PHY devices 110 a and 110 b mayalso support exchange and negotiation of speed capabilities foridentifying and selecting communication parameters such as speed andduplex mode.

In various embodiments of the invention, the PHY devices 110 a and 110 bmay comprise suitable logic, circuitry, and/or code that may enableasymmetric data rates that may support energy Efficient Ethernet. ThePHY devices 110 a and/or 110 b may enable transmission and/or receptionat a high(er) data rate in one direction and transmission and/orreception at a low(er) data rate in the other direction. In oneexemplary embodiment of the invention, the remote link partner 104 maycomprise a multimedia server and the local link partner 102 may comprisea multimedia client. In this regard, the remote link partner 104 maytransmit multimedia data, for example, to the local link partner 102 athigh(er) data rates while the local link partner 102 may transmitcontrol or auxiliary data associated with the multimedia content atlow(er) data rates. Other exemplary embodiments of the invention maycomprise switches, aggregation switches and routers.

A change in rate such as stepping up in rate or stepping down in ratemay occur asymmetrically among the PHY devices 110 a and/or 110 b. Forexample, a data rate for traffic in one direction corresponding to atransmitter on the PHY device 110 a and a receiver on the PHY device 110b may step down while the data rate in the opposite direction on thesame channel may be reduced or it may remain the same. Moreover, in someembodiments of the invention, one or more of the PHY devices may stepdown to a rate of zero. For example, a data rate in one direction may bezero while a data rate in the opposite direction may be a full rate oran intermediate rate.

In various embodiments of the invention, for a data rate transition, alink partner, for example, the link partner 102, may utilize a byte ofan Ethernet frame on which to transition a rate. In this regard, thelink partner 102 may transition the rate just after transmitting thedesignated byte and the link partner 104 may transition just afterreceiving the designated byte. In this manner, data rate transitions ona link may occur in mid-frame. This technique may be very useful onserial type interfaces like a 10GBASE-KR or any of the opticalinterfaces. Additionally, in accordance with an embodiment of theinvention, the data rate may transition on an LDPC frame boundary. Thismay be useful for systems such as a 10GBASE-T PHY that splits anEthernet packet into LDPC frames or any other PHY that splits packetsinto frames.

The data transmitted and/or received by the PHY devices 110 a and 110 bmay be formatted in accordance with the well-known OSI protocolstandard. The OSI model partitions operability and functionality intoseven distinct and hierarchical layers. Generally, each layer in the OSImodel is structured so that it may provide a service to the immediatelyhigher interfacing layer. For example, layer 1, or physical layer, mayprovide services to layer 2 and layer 2 may provide services to layer 3.The data transmitted may comprise frames of Ethernet media independentinterface (MII) data which may be delimited by start of stream and endof stream delimiters, for example. The data transmitted may alsocomprise IDLE symbols that may be communicated between frames of data,during inter frame gap (IFG)).

In an exemplary embodiment of the invention illustrated in FIG. 1, thehosts 106 a and 106 b may represent layer 2 and above, the MACcontrollers 108 a and 108 b may represent layer 2 and above and the PHYdevices 110 a and 110 b may represent the operability and/orfunctionality of layer 1 or the physical layer. In this regard, the PHYdevices 110 a and 110 b may be referred to as physical layertransmitters and/or receivers, or physical layer transceivers, PHYtransceivers, PHYceivers, or PHY, for example. The hosts 106 a and 106 bmay comprise suitable logic, circuitry, and/or code that may enableoperability and/or functionality of the upper OSI layers for datapackets that are to be transmitted over the cable 112. Since each layerin the OSI model provides a service to the immediately higherinterfacing layer, the MAC controllers 108 a and 108 b may provide thenecessary services to the hosts 106 a and 106 b to ensure that packetsare suitably formatted and communicated to the PHY devices 110 a and 110b. During transmission, each layer may add its own header to the datapassed on from the interfacing layer above it. However, duringreception, a compatible device having a similar OSI stack may strip offthe headers as the message passes from the lower layers up to the higherlayers.

The PHY devices 110 a and 110 b may be configured to handle all thephysical layer requirements, which include, but are not limited to,packetization, data transfer and serialization/deserialization (SERDES),in instances where such an operation may be required. Data packetsreceived by the PHY devices 110 a and 110 b from MAC controllers 108 aand 108 b, respectively, may comprise data and header information foreach of the above six functional layers. The PHY devices 110 a and 110 bmay be configured to encode data packets that are to be transmitted overthe cable 112 and/or to decode data packets received from the cable 112.

The MAC controller 108 a may comprise suitable logic, circuitry, and/orcode that may enable handling of data link layer, layer 2, operabilityand/or functionality in the local link partner 102. Similarly, the MACcontroller 108 b may comprise suitable logic, circuitry, and/or codethat may enable handling of layer 2 operability and/or functionality inthe remote link partner 104. The MAC controllers 108 a and 108 b may beconfigured to implement Ethernet protocols, such as those based on theIEEE 802.3 standard, for example. Notwithstanding, the invention is notlimited in this regard.

The MAC controller 108 a may communicate with the PHY device 110 a viaan interface 114 a and with the host 106 a via a bus controllerinterface 116 a. The MAC controller 108 b may communicate with the PHYdevice 110 b via an interface 114 b and with the host 106 b via a buscontroller interface 116 b. The interfaces 114 a and 114 b correspond toEthernet interfaces that comprise protocol and/or link managementcontrol signals. The interfaces 114 a and 114 b may be multi-rateinterfaces and/or media independent interfaces (MII). The bus controllerinterfaces 116 a and 116 b may correspond to PCI or PCI-X interfaces.Notwithstanding, the invention is not limited in this regard.

In operation, the PHY devices 110 a and 110 b may operate within, forexample, a 1 Gbps or 10 Gbps network. Conventionally, the PHY devices110 a and 110 b may transmit data in a symmetric manor such that a datarate in one direction may be the same as a data rate in an oppositedirection, regardless of the level of offered traffic in each direction.However, there may be instances when traffic may be greater in onedirection and operating with symmetric data rates may be inefficient. Invarious embodiments of the invention, the local link partner 102 and/orthe remote link partner 104 may be enabled negotiate and/or coordinatedifferent rates for different directions of traffic flow via theEthernet link 112. In this regard, based on various factors that may,for example, power consumption and/or energy efficiency, the localpartner 102 may be configured to transmit data to a remote partner 104at a first data rate over one or more channels, while the remote partner104 may transmit data to the local partner 102 at a second data rateover one or more other channels. The PHY devices 110 a and/or 110 b, MACdevices 108 a and 108 b and/or the hosts 106 a and/or 106 b may beenabled to consume less energy and/or utilize fewer resources as aresult of lower transmission and/or reception rates.

In an exemplary embodiment of the invention, asymmetric traffic over anEthernet link may comprise multimedia data that may be downloaded from amultimedia server, for example, remote link partner 104 to aset-top-box, For example, local link partner 102. In this manner, themulti-media traffic from remote link partner 104 to the local linkpartner 102 may be transmitted at a higher data rate than, for example,signaling and/or control information transmitted from the local linkpartner 102 to the remote link partner 104. In this manner, the remotelink partner 104 may be an uplink partner and the local link partner 102may be a downlink partner.

FIG. 2 is a block diagram illustrating an exemplary Ethernet overtwisted pair PHY device architecture, in accordance with an embodimentof the invention. Referring to FIG. 2, there is shown a link partner 200which may comprises an Ethernet over twisted pair PHY device 202, a MACcontroller 204, a host 206, an interface 208, and a bus controllerinterface 210. The PHY device 202 may be an integrated device which maycomprise a multirate physical layer block 212, one or more transmitters214, one or more receivers 220, a memory 216, a memory interface 218,one or more input/output interfaces 222 and the channels 224.

The PHY device 202 may be an integrated device that may comprise amulti-rate physical layer block 212, one or more transmitters 214, oneor more receivers 220, a memory 216, a memory interface 218, and one ormore input/output interfaces 222. The operation of the PHY device 202may be the same as or substantially similar to that of the PHY devices110 a and 110 b disclosed in FIG. 1. In this regard, the PHY device 202may provide layer 1 (physical layer) operability and/or functionalitythat enables communication with a remote PHY device. Similarly, theoperation of the MAC controller 204, the host 206, the interface 208,and the bus controller 210 may be the same as or substantially similarto the respective MAC controllers 108 a and 108 b, hosts 106 a and 106b, interfaces 114 a and 114 b, and bus controller interfaces 116 a and116 b as described in FIG. 1. The MAC controller 204 may comprise aninterface 204 a that may comprise suitable logic, circuitry, and/or codeto enable communication with the PHY device 202 via the interface 208.

The multi-rate physical layer block 212 in the PHY device 202 maycomprise suitable logic, circuitry, and/or code that may enableoperability and/or functionality of physical layer requirements. In thisregard, the multi-rate physical layer block 212 may enable generatingthe appropriate link discovery signaling utilized for establishingcommunication with a remote PHY device in a remote link partner. Themulti-rate physical layer block 212 may communicate with the MACcontroller 204 via the interface 208. In one aspect of the invention,the interface 208 may be a media independent interface (MII) and may beconfigured to utilize a plurality of serial data lanes for receivingdata from the multi-rate physical layer block 212 and/or fortransmitting data to the multi-rate physical layer block 212. Themulti-rate physical layer block 212 may be configured to operate in oneor more of a plurality of communication modes, where each communicationmode may implement a different communication protocol. Thesecommunication modes may comprise, for example, Ethernet over twistedpair standards 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-T, and othersimilar protocols that utilize multiple channels between link partners.The multi-rate physical layer block 212 may be configured to operate ina particular mode of operation upon initialization or during operation.For example, a rate (such as 10 Mbps, 100 Mbps, 1000 Mbps, or 10 Gbps)and/or mode (duplex or simplex) for transmitting information may benegotiated between link partners. For example, a physical layer protocolsuch as out-of-band channels, Q-ordered sets or a preamble may beutilized or a frame based protocol such as LLDP may be utilized todetermine a rate or mode.

The multi-rate physical layer block 212 may be coupled to memory 216through the memory interface 218, which may be implemented as, forexample, a serial interface or a bus. Notwithstanding, the memory 216may comprise suitable logic, circuitry, and/or code that may enablestorage or programming of information that includes parameters and/orcode that may effectuate the operation of the multi-rate physical layerblock 212. The parameters may comprise configuration data and the codemay comprise operational code such as software and/or firmware, but theinformation need not be limited in this regard. Moreover, the parametersmay include adaptive filter and/or block coefficients for use by themulti-rate physical layer block 212, for example

Each of the transmitters 214 a, 214 b, 214 c, 214 d may comprisesuitable logic, circuitry, and/or code that may enable transmission ofdata from the link partner 200 to a remote link partner via, forexample, the cable 112 in FIG. 1. The receivers 220 a, 220 b, 220 c, 220d may comprise suitable logic, circuitry, and/or code that may enablereceiving data from a remote link partner. Each of the transmitters 214a, 214 b, 214 c, 214 d and receivers 220 a, 220 b, 220 c, 220 d in thePHY device 202 may correspond to a channel that may comprise the cable112. In this manner, a transmitter/receiver pair may interface with eachof the channels 224 a, 224 b, 224 c, 224 d. Conventionally, transmitterreceiver pairs such as 214 a and 220 a, 214 b and 220 b, 214 c and 220 cand/or 214 d and 214 d may each transmit and receive data at the samedata rate. For example, at data rates such as 100 Mbps, 1 Gbps, 10 Gbps.In various embodiments of the invention, a transmitter and receiverwithin one or more pairs may be enabled to operate at differentcommunication rates over one or more channels based, for example, onenergy efficiency, power consumption, link utilization, current load,expected or predicted load, and/or other factors.

The input/output interfaces 222 may comprise suitable logic circuitry,and/or code that may enable the PHY device 202 to impress signalinformation onto a physical medium comprising a channel, for example atwisted pair channel comprising the cable 112 disclosed in FIG. 1.Consequently, the input/output interfaces 222 may, for example, provideconversion between differential and single-ended, balanced andunbalanced, signaling methods. In this regard, the conversion may dependon the signaling method utilized by the transmitter 214, the receiver220, and the type of medium comprising the channel. Accordingly, theinput/output interfaces 222 may comprise one or more baluns and/ortransformers and may, for example, enable transmission over a twistedpair. Additionally, the input/output interfaces 222 may be internal orexternal to the PHY device 202. In this regard, if the PHY device 202comprises an integrated circuit, then “internal” may, for example, referto being “on-chip” and/or sharing the same substrate. Similarly, if thePHY device 202 comprises one or more discrete components, then“internal” may, for example, refer to being on the same printed circuitboard or being within a common physical package.

In operation, the link partner 200 may be configured to transmit and/orreceive traffic at different data rates. In this regard, the PHY device202 may coordinate and/or negotiate with a remote link partner totransmit data at a first data rate and receive data at a second datarate. Transmission and/or reception data rates may be increased ordecrease according to one or more factors that affect power consumptionand/or energy efficiency. For example, link statistics such as linkutilization, bit error rate (BER) and/or packet error rate (PER) mayindicate that a data rate may be increased or decreased. In addition,system workload, subsystem functions such as bus utilization, queuedepths and/or rate of change of queues in a switch may be monitored forexample. In this regard, data rates for data travelling in one directionmay be lowered to a level that may enable a more efficient use ofenergy. For example, link partner 200 s transmission data rate may belowered to zero while its reception rate may be at full rate or anintermediate/sub-rate. Moreover, various functions and/or components ofthe link partner 200 and/or channels 224 may be simplified, shared oreliminated as a result of reduced data rates.

In an exemplary embodiment of the invention, a multimedia server maycomprise the link partner 200 that may transmit multimedia traffic at afirst higher data rate to a client and/or may receive control and/orsignaling traffic at a second lower data rate from the client. In thismanner, portions of the multi-rate PHY block, the transmitters 214, thereceivers 220, the hybrids 226, and/or the interfaces 222 may be powereddown (or placed in a low(er) power state). Accordingly, powerconsumption may be reduced in the host 206 and/or MAC controller 204based on reduced data rates.

FIG. 3A is a block diagram illustrating asymmetric data rates enablingreduced power consumption and improved energy efficiency, in accordancewith an embodiment of the invention. Referring to FIG. 3A there is shownthe link partners 102 and 104 as described with respect to FIG. 1, withthe data rates between the link partners 102 and 104 represented byarrows 302 and 304. The size of the arrow represents a relative datarate for data traveling in the direction corresponding to the arrow.Thus, in the exemplary embodiment of the invention, a first data rate302 from the link partner 102 to the link partner 104 may be lower thana second data rate 304 from the link partner 104 to the link partner102. For example, the link partner 104 may be a video server or dataserver. For various time instants the data rate 304 may be, for example,at 90% of full rate while the data rate 302 in the opposite directionmay be only at 10% of full rate.

FIG. 3B is a block diagram of an exemplary system that may utilizeasymmetric data rates to reduce power consumption, in accordance with anembodiment of the invention. Referring to FIG. 3B, there is shown anEthernet switch 322, a file server 324, and Ethernet link 312, the datarate 302 and the data rate 304.

The Ethernet switch 322 and file server 324 may comprise Ethernet linkpartners that are similar to or substantially the same as the linkpartners 102 and 104 respectively. In addition, the Ethernet link 312may be similar and/or substantially the same as the Ethernet link 112.The data rate 302 and data rate 304 are described with respect to FIG.3A.

The Ethernet switch 322 and file server 324 may be enabled to exchangedata with asymmetric data rates. For example, the file server 324 maydownload large multi-media files, requiring a high bandwidth via theEthernet switch 322. The Ethernet switch 322 may transmit control and/orauxiliary data associated with the multimedia content at a low(er) datarate 302 to the file server 324.

In operation, aspects of the invention may enable negotiation betweenthe link partners 322 and/or 324 to determine the rates 302 and/or 304.The link partners 322 and/or 324 may assess factors that may affectpower consumption such as an amount of data stored within bufferswaiting for transmission for example. The link partners 322 and/or 324may agree upon stepping up or stepping down a data rate in one or moredirections prior to and/or during transmission. For example, based on anagreed upon one or more determined rates, the link partner 322 may beconfigured to transmit at data rate 302 and receive at a data rate 304while the link partner 324 may be configured to transmit at data rate304 and receive at data rate 302. In this regard, the link partner 322may be a downlink partner and the link partner 324 may be an uplinkpartner.

In this manner, energy efficiency may be improved within the linkpartners 322 and/or 324 as compared with link partners that utilizesymmetric data rates. For example, the link partner 322 may compriseelements such as the host 106 a, the medium access control (MAC)controller 108 a, and the PHY device 110 a shown in FIG. 1. Variouscomponents and/or functions within these elements may be set to alow(er) power state; they may be shared and/or may be eliminated whenlower data rates are utilized. Accordingly, significant power savingsmay be achieved within link partners 322 and/or 324 in addition to powersavings on the Ethernet link 112.

FIG. 4 is a flow chart illustrating exemplary steps for communicatingbetween link partners via one or more channels utilizing asymmetric datarates, in accordance with an embodiment of the invention. Referring toFIG. 4, after start step 402, in step 404, one or both of multi-ratelink partners 102 and 104 communicating via one or more channels 224 a,224 b, 224 c and 224 d, may monitor one or more factors that affectpower consumption and/or energy efficiency and may determine that a datarate in at least one direction may be increased or decreased. In step406, in instances when the data rate after the increase or decrease isdifferent in each direction (asymmetrical), exemplary steps may proceedto step 408. In step 408, a link partner 102 transmitting in thedirection of a data rate change may communicate at a new data rate tothe receiving link partner 104 and the receiving link partner 104 mayacknowledge the new data rate for one direction. In step 410, the linkpartners 102 and/or 104 may configure circuitry, timing loops and/orparameters that support transmission and reception in the direction ofthe rate change.

In step 412, the link partners 102 and 104 may communicate utilizingasymmetric data rates. Step 414 may be an end of exemplary steps. Instep 406, in instances when the data rate after the increase or decreaseis the same in both directions (symmetrical), exemplary steps mayproceed to step 416. In step 416, the multi-rate link partners 102 and104 may negotiate a change in data rate wherein each link partner 102and 104 may, in each direction, agree or disagree to and/or acknowledgethe rate change. In step 418, the multi-rate link partners 102 and 104may configure circuitry, timing loops and/or parameters for changing thedata rate in both directions. In step 420, the link partners 102 and 104may communicate utilizing symmetric data rates. Step 414 may be the endof exemplary steps.

FIG. 5 is a data flow diagram illustrating an exemplary method forchanging data rate in an asymmetric network configuration, in accordancewith an embodiment of the invention. Referring to FIG. 5 there is shownthe link partners node A 102 (twice) and node B 104. Data trafficbetween node A 102 and node B 104 may be represented by the shaded areas502, 504 and 510. Physical layer signaling traffic between node A 102and node B 104 may be represented by the shaded area 506 and anacknowledgement signal (ACK) or negative acknowledgement signal (NACK)may be represented by broken line 508.

Prior to time instant t1, the node A 102 and node B 104 may be eachtransmitting at a first data rate. In this regard, the rate for datatraffic 502 transmitted by the node A 102 and the data traffic 504transmitted by the node B 104 may be the same, for example, a full rate.Prior to time instant t1, the node A 102 may determine to change itsdata rate, for example, to a half rate. At time instant t1, the node A102 may begin transmitting physical layer signaling 506 which maycomprise a request to lower the data rate from full rate to half ratefor data traffic travelling in the direction from the node A 102 to thenode B 104. In some exemplary embodiments of the invention, the requestsignal 506 may be transmitted via physical layer signaling together withpackets of the data traffic 502. Packet based signaling generated byhigher layer protocols may be utilized. Notwithstanding, physical layersignaling may enable a faster data rate transition.

After the data rate change request 506 arrives at the node B 104, thenode B 104 may prepare for changing to its data rate in the directionwhich it is receiving data. Notwithstanding, the node B 104 may continuetransmitting the data traffic 504 without disruption since it may not bechanging data rate in the direction of its transmission. At time instantt2, the node B 104 may acknowledge (ACK) reception of the data ratechange request 506 via physical layer signaling 508 sent together withpackets for data traffic 504. In this regard, the ACK 508 may becommunicated, for example, via a distinct idle symbol, withoutinterrupting transmission 504. The node B 104 may begin to prepare itsreceiving circuitry, parameters and/or timing loops for reception ofdata traffic at the half rate. At time instant t3, the ACK 506 mayarrive at node A 102. Accordingly, at time instant t4, the node A 102may begin transmission 510 at the half rate. Since the node B 104 maynot change rate in the direction of its transmission, the node A 102 maybegin transmitting data traffic 510 without a time delay. For example,the node A 102 may not have to wait for the node B 104 to complete itstransmission of data traffic 504. Moreover, the node A may not have towait for the node B to acknowledge the request for lowering the datarate or to prepare circuitry, parameters and/or timing loops fortransmission at a half rate. In a symmetric data rate system, both linknodes 102 and 104 may need to be able to transmit at lower data ratesbefore a more energy efficient, low(er) power operation may be achieved.

In various embodiments of the invention, an Ethernet network maycomprise network nodes, for example, multi-rate link partners 102 and104, coupled via an Ethernet link 112. The Ethernet link may compriseone or more channels such as 224 a, 224 b, 224 c and 224 d. In addition,the multi-rate link partners 102 and/or 104 may comprise componentscorresponding to the one or more channels 224 a, 224 b, 224 c and 224 d.In various embodiments of the invention, the multi-rate link partners102 and 104 may be enabled to communicate in a first direction at afirst data rate 302 and in a second direction at a second data rate 304over one or more of the plurality of channels. Moreover, the multi-ratelink partners 102 and/or 104 may determine the first data rate 302and/or the second data rate 304 and may agree upon the determined datarates 302 and/or 304 based on negotiations. The multi-rate link partners102 and/or 104 may be configured accordingly. In this regard, theconfigured multi-rate link partners 102 and/or 104 may communicate viathe one or more channels 224 a, 224 b, 224 c and 224 d in an asymmetricmanor according to the first and/or second determined data rates 302and/or 304.

In various embodiments of the invention, the first and second data rates302 and 304 may be the same or may be different. Additionally, the firstand/or second data rates 302 and 304 may be modified before, duringand/or after communication via the one or more channels 224 a, 224 b,224 c and 224 d. In instances where the first data rate 302 and/or thesecond data rate 304 is low(er) on one or more channels 224 a, 224 b,224 c and 224 d, power levels for one or more corresponding componentsmay be low(er) and as such may derive significant power savings. Thecorresponding components may be located within multi-rate link partner102 and/or 104 within elements such as a multi-rate physical interface(PHY) 202, a medium access controller (MAC) 204 and a host 206 as wellas within the Ethernet link 112. In some embodiments of the invention,the multi-rate link partners 102 and 104 may comprise a multimediasystem wherein high bandwidth multimedia data may be transmitted in afirst direction at a first data rate 304 for example from a multimediaserver to a client and corresponding low bandwidth control informationmay be transmitted in a second direction at a second data rate 302 fromthe client to the multimedia server.

In an embodiment of the invention, an Ethernet network 100 may comprisemulti-rate link partners 102 and 104 that may be operable to communicatesymmetrically and/or asymmetrically. In this regard, the multi-rate linkpartners 102 and 104 may communicate via any of a plurality of channelson a link that may couple the multi-rate link partners 102 and 104. Inaddition, the multi-rate link partners 102 and 104 may monitor one ormore factors that may affect their power consumption and/or energyefficiency. During operation, an uplink communication rate 302 and/or adownlink communication rate 304 of the one or more multi-rate linkpartners 102 and/or 104, may be configured to enable asymmetrical datarate operation via any of the plurality of channels 224 a, 224 b, 224 cand 224 d based on the monitoring. The monitored factors may comprise,for example, prior or current data rates, bit error rate (BER), packeterror rate (PER) and/or latency, for example. In accordance with anembodiment of the invention, the multi-rate link partners 102 and 104may comprise, for example, a twisted pair PHY, an optical PHY or abackplane PHY. In order to reduce power consumption and/or improveenergy efficiency, one or more of the uplink communication rate 302and/or the downlink communication rate 304 may be lowered. Thecommunication rates 302 and/or 304 may be transitioned to a lower orhigher data rate at, for example, designated byte boundaries and/or atLDPC frame boundaries. In this manner, the power consumption may bereduced by the multi-rate PHY 110 a and/or 110 b, the host computer 106a and/or 106 b and/or the MAC controller 108 a and/or 108 b.

Another embodiment of the invention may provide a machine and/orcomputer readable storage and/or medium, having stored thereon, amachine code and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for a methodand system for asymmetric operation in a network node in an energyefficient Ethernet network.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system or in a distributed fashion where different elements arespread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method, comprising: transmitting, in a firsttransmission direction from a first link partner to a second linkpartner, packets of data at a first data rate, said second link partnerbeing coupled to said first link partner via a cable communicationmedium; transmitting, in said first transmission direction from saidfirst link partner to said second link partner, an asymmetric request tolower a data rate for use in said first transmission direction from saidfirst link partner to said second link partner from said first data rateto a second data rate lower than said first data rate, wherein saidasymmetric request is transmitted via one or both of physical layersignaling and packet based signaling generated by higher layerprotocols, said asymmetric request being generated based on monitoringof one or more factors that relate to an efficiency of transmission insaid first transmission direction; and after transmission of saidasymmetric request, configuring said first link partner to communicatein said first transmission direction at said second data rate, while asecond transmission direction from said second link partner to saidfirst link partner continues to communicate at said first data rate. 2.The method according to claim 1, wherein said one or more factorsinclude one or more of prior data rates, current data rates, bit errorrate, packet error rate and latency.
 3. The method according to claim 1,wherein said one or more factors include one or more of data load, queuedepths, queue change rates, tasks assigned bus operations and layer twoand above control policy.
 4. The method according to claim 1, whereinsaid configuring comprises configuring one of a twisted pair physicallayer device, optical physical layer device and backplane physical layerdevice.
 5. The method according to claim 1, wherein said configuringcomprises configuring a media access control device or a host device. 6.The method according to claim 1, wherein said second data rate is zero.7. The method according to claim 1, wherein said configuring comprisesreducing a data rate of one of a plurality of channels in said firsttransmission direction to zero.
 8. The method according to claim 1,wherein said configuring comprises transitioning from said first datarate to said second data rate at a designated byte boundary or an LDPCframe boundary.
 9. A system for energy efficient networking, the systemcomprising: one or more circuits in a first link partner that iscommunicatively coupled to a second link partner via a cablecommunication medium, said one or more circuits operable to: transmit,in a first transmission direction from said first link partner to saidsecond link partner, packets of data at a first data rate, said secondlink partner being coupled to said first link partner via a cablecommunication medium; transmit, in said first transmission directionfrom said first link partner to said second link partner, an asymmetricrequest to lower a data rate for use in said first transmissiondirection from said first link partner to said second link partner fromsaid first data rate to a second data rate lower than said first datarate, wherein said asymmetric request is transmitted via one or both ofphysical layer signaling and packet based signaling generated by higherlayer protocols, said asymmetric request being generated based onmonitoring of one or more factors that relate to an efficiency oftransmission in said first transmission direction; and aftertransmission of said asymmetric request, configure said first linkpartner to communicate in said first transmission direction at saidsecond data rate, while a second transmission direction from said secondlink partner to said first link partner continues to communicate at saidfirst data rate.
 10. The system according to claim 9, wherein said oneor more factors include one or more of prior data rates, current datarates, bit error rate, packet error rate and latency.
 11. The systemaccording to claim 9, wherein said one or more factors include one ormore of data load, queue depths, queue change rates, tasks assigned busoperations and layer two and above control policy.
 12. The systemaccording to claim 9, wherein said one or more circuits configure one ofa twisted pair physical layer device, optical physical layer device andbackplane physical layer device.
 13. The system according to claim 9,wherein said one or more circuits configure a media access controldevice or a host device.
 14. The system according to claim 9, whereinsaid second data rate is zero.
 15. The system according to claim 9,wherein said one or more circuits reduce a data rate of one of aplurality of channels in said first transmission direction to zero. 16.The system according to claim 9, wherein said one or more circuitsconfigure a transition from said first data rate to said second datarate at a designated byte boundary or an LDPC frame boundary.
 17. Amethod, comprising: transmitting, in a first transmission direction froma first link partner to a second link partner, packets of data at afirst data rate, said second link partner being coupled to said firstlink partner via a cable communication medium; monitoring one or morefactors that affect an efficiency of transmission in said firsttransmission direction; concurrently with said transmitting packets ofdata, transmitting from said first link partner to said second linkpartner, via physical layer signaling, a request to change a data ratefrom said first data rate to a second data rate in said first directionof transmission; and configuring said first link partner forcommunication at said second data rate in said first direction oftransmission, while a second transmission direction from said secondlink partner to said first link partner continues to communicate at saidfirst data rate, said configuring enabling asymmetrical data rateoperation between said first link partner and said second link partnerover said cable communication medium.
 18. The method of claim 17,wherein said configuring comprises configuring one of a twisted pairphysical layer device, optical physical layer device and backplanephysical layer device.
 19. The method of claim 17, wherein saidconfiguring comprises configuring a media access control device or ahost device.
 20. The method of claim 17, wherein said configuringcomprises reducing a data rate of one of a plurality of channels in saidfirst transmission direction to zero.